<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
       var a = [1,2,3];
       console.log(a[5]);
       a[10]=100;
       console.log(a);

       a.push("a");
       alert(a);
       var f = a.pop();
       alert(f);
    </script>
</head>
<body>
</body>
</html>